KR20010040542A - Improved method for making mixed high purity (meth)acrylic anhydrides - Google Patents

Abstract

The present invention is made by reacting alkaline (meth) acrylic acid of formula (II) and chloroformate of formula (III) in the absence of an amine in an aqueous medium with a molar ratio of chloroformate (III) / alkaline (meth) acrylate (II) of at least 1.15. A method for preparing mixed (meth) acrylic anhydride of formula (I).

Description

IMPROVED METHOD FOR MAKING MIXED HIGH PURITY (METH) ACRYLIC ANHYDRIDES

The present invention is a method for producing a mixed anhydride represented by the formula (I)

(Wherein

R ¹ represents H or CH ₃ ,

R ² represents an alkyl, alkenyl, aryl, alkaryl or aralkyl moiety)

A method of reacting an alkali metal (meth) acrylate of formula (II) with a chloroformate of formula (III)

(Wherein

R ¹ is as described above,

M is an alkali metal),

Wherein R ² is as described above.

Mixed anhydrides are mild acylating agents and their use has traditionally been used. And acid chlorides It has been described by peptide synthesis in place of.

In addition, the only adducts produced by the mixed anhydrides of formula (I) in the acylation reaction are carbon dioxide and alcohol R ² OH, which are easier to remove than (meth) acrylic acid or hydrochloric acid.

Methods of synthesizing non-acrylic mixed anhydrides described in the literature are generally described in J. Am. Chem. Soc. 73, 3547, 1951, based on the method described by Vaughan. Mixed anhydrides here are synthesized at low temperature (generally below 0 ° C.) by equimolar reaction between alkyl chloroformate and tertiary carboxylic acid amine in a solvent medium (tetrahydrofuran, acetone, toluene, chloroform, etc.). In the solvent medium, in addition to the need for operation at cryogenic temperatures, a major limitation of this process lies in the fact that the trialkylammonium chloride which precipitates in the medium needs to be separated off by filtration.

Bull. Chem. Soc. Jap. 1968, 41, 2521-3, Harada and Konda, in the examples, show carboethoxymet by reaction between potassium methacrylate and ethyl chloroformate in a solvent medium (chloroform) at 0 ° C. in the presence of pyridine. Acrylic Anhydride:

Describes the synthesis of

Synthesis of carboxymethacrylic anhydride is also described in French Patent Application FR-A-2 212 340, starting with triethylammonium methacrylate and ethyl chloroformate as solvent in solvent medium (acetonitrile).

Synthesis of non-acrylic mixed anhydrides is described in DE-C-1 133 727 as a reaction between carboxylates and chloroformates with a molar ratio of chloroformate / carboxylate of 0.95 to 1.10.

The processes described in the literature usually relate to non-acrylic mixed anhydrides, with many drawbacks in this case, the main drawbacks being the use of a calculated or catalytic amount of solvent for carboxylic acids and the use of amines. It is also a drawback that the alkylammonium chloride must be separated by filtration.

In most of the processes described in the literature, reagents (II) and (III) are used in equimolar ratios or in molar ratios of 0.95 to 1.1. Trace amounts of symmetric anhydride under these conditions Mixed (meth) acrylic anhydrides containing

Can be obtained, wherein R ¹ is as defined above. This method is inconvenient, especially when trying to synthesize carboxyalkoxy (meth) acrylic anhydrides containing trace amounts of methacrylic anhydride. Applicant has surprisingly been able to solve this problem by modifying the conditions of the reaction between compounds (II) and (III), in particular by carrying out this synthesis with a molar ratio of compound (III) / compound (II) of at least 1.15. Found that there is.

Subject of the present invention is the aforementioned compound (II), characterized in that it is carried out in the absence of an amine in an aqueous medium, with a molar ratio of chloroformate (III) / alkali metal (meth) acrylate (II) of at least 1.15. It is a manufacturing method of high purity mixed (meth) acrylic anhydride (I) by reaction between and (III).

In general, the reaction is carried out with compounds (II) and (III) as follows:

R ² is C ₁ -C ₄₀ alkyl, C ₂ -C ₄₀ alkenyl, phenyl, phenyl (C ₁ -C ₄₀ alkyl) and (C ₁ -C ₄₀ alkyl) phenyl residues,

M represents sodium or potassium.

Particularly applicable are anhydrides of the formula I (wherein R ² represents C ₁ -C ₄₀ alkyl such as ethyl, n-propyl, isopropyl, n-butyl or isobutyl), and preferred mixed anhydrides of the invention Make up a series. These are mild acylating agents which can very advantageously replace methacrylic anhydride or (meth) acryloyl chloride, which produce methacrylic acid or hydrochloric acid upon acylation.

In the process of the invention, for example By-products of form

To limit the formation, the molar ratio of chloroformate (III) / alkali metal (meth) acrylate (II) can be from 1.15 to 2, preferably from 1.5 to 1.7. Above 1.15, substantial improvements in selectivity and yield were observed. Thus, when the synthesis of carboethoxymethacrylic anhydride is carried out by a reaction between sodium methacrylate and ethyl chloroformate, a decrease in the formation of methacrylic anhydride and by-products is observed. In addition, high molar ratios are preferred in terms of selectivity but disadvantageous in terms of production efficiency.

The reaction according to the invention is advantageously carried out at temperatures of -10 to +30 ° C, preferably of +10 to +20 ° C.

According to one embodiment of the present invention, alkali metal (meth) acrylate (II) is prepared as an aqueous solution by neutralizing (meth) acrylic acid with peroxide MOH, and then chloroformate (III) is mixed with alkali metal (meth) acrylate. (Wherein the molar ratio of MOH / (meth) acrylic acid is 1 to 1.5, in particular 1 to 1.1, and the weight ratio of water / alkali metal (meth) acrylate (II) is 1.5 to 7, in particular 1.5 to 2 being).

According to one particularly advantageous property of the invention, the reaction between alkali metal (meth) acrylate (II) and chloroformate (III) is dissolved in a polymeric support such as styrene-divinylbenzene copolymer or crosslinked polyvinylpyridine resin. Or in the presence of a fixed phase transfer catalyst, which catalyst is used at a rate of 0.001 to 0.02 moles, in particular 0.005 to 0.01 moles per mole of alkali metal (meth) acrylate (II).

The phase transfer catalyst is advantageously selected from quaternary ammonium salts, phosphonium salts and crown ethers.

Examples of tetravalent ammonium salts include the following:

(Wherein

Each of R ⁴ to R ⁷ is C ₁ -C ₄₀ alkyl such as CH ₃ , C ₂ H ₅ , C ₄ H ₉ , C ₈ H ₁₇ and C ₁₆ H ₃₃ , or aryl such as phenyl, or benzyl Alkyl,

X is one of Cl, Br, I, OH and HSO ₄ , in particular tetramethylammonium chloride, benzyltrimethylammonium chloride, benzyltri-n-butylammonium chloride, tetra-n-butylammonium chloride, tetra-n-butyl bromide One of ammonium, methyltrioctylammonium bromide and tetra-n-butylammonium hydrogen sulfate,

-Examples of phosphonium salts, , , , Can be mentioned,

-As examples of crown ethers, 18-crown-6 and dibenzoyl-18-crown-6 can be mentioned).

Operation in the presence of a phase transfer catalyst substantially increases the reaction (3 to 5 hours as opposed to 15 hours without catalyst).

The reaction according to the invention is generally carried out with stirring in a jacketed reactor which is isothermally controlled while precisely controlling the temperature. The crude reaction mixture is separated into two phases by precipitation when stirring stops (or into three phases when immobilized on the polymerization support using a phase transfer catalyst). The reaction progress is monitored by taking samples of the aqueous phase regularly and analyzing the residual alkali metal (meth) acrylate (II). The reaction is considered complete when the conversion of alkali metal (meth) acrylate (II) is greater than 95%.

At the end of the reaction, the phases of the two-phase or three-phase reaction mixture are separated by precipitation at room temperature, advantageously washed at room temperature (amount: 20-100% of the weight of the organic phase, preferably 30-40%), and then The organic phase comprising mixed anhydride (I) and excess chloroformate (III) is separated off in vacuo at a temperature of up to 35 ° C. Thus mixed anhydrides are obtained in very high purity.

The ratio of 500 to 5000 ppm, preferably 500 to 1000 ppm, relative to alkali metal (meth) acrylate (II)-or its precursor (meth) acrylic acid-can be immobilized by introducing one or more polymerization inhibitors into the reaction medium. There is a need.

Examples of polymerization inhibitors include hydroquinone methyl ether, hydroquinone, phenothiazine and di-tert-butyl-para-cresol.

However, the following examples illustrate the invention without limiting its scope. In this embodiment, the percentages are based on weight unless otherwise indicated.

Example 1

408 g of an aqueous 26.5% sodium methacrylate solution in which 900 mg hydroquinone ether is introduced is placed in a jacket reactor whose temperature is maintained by an isothermally controlled water circulation aid at 20 ° C., followed by 162.8 g of chloroform acid over 5 minutes. Ethyl (molar ratio of ethyl chloroformate / sodium methacrylate: 1.5: 1) is introduced.

The heterogeneous mixture is stirred for 15 hours. The phases are then separated by precipitation at room temperature. To remove excess chloroformate, the organic phase is dried over calcium sulphate and the volatiles are removed under vacuum at a temperature below 35 ° C.

NMR purity of carboethoxymethacrylic anhydride is 95%, remaining 5% is methacrylic anhydride 153 g of a product consisting of (yield: 96.7%) are obtained.

Examples 2-5

Example 1 is repeated while adjusting the temperature and molar ratio of ethyl chloroformate / sodium methacrylate.

The results are shown in Table 1.

Example 2 3 4 5 Molar ratio of ethyl chloroformate / sodium methacrylate 1.5 1.5 1.5 3 Temperature (℃) 5 25 35 15 Reaction time (h) 30 8 7 24 % Conversion of sodium methacrylate 81 90.3 97.4 98.5 Composition (wt%) of organic phase separated by precipitation, ethyl chloroformate, carboethoxymethacrylic anhydride, methacrylic anhydride, ethanol, water 39.7555 〈10.3 29637 〈10.2 22.5651110.1 63352 Composition (wt%) of organic phase from which volatiles were removed, carboethoxymethacrylic anhydride, methacrylic anhydride 919 9010 85.514.5 94.55.5

Example 6

The process is carried out in the same apparatus as in Example 1.

445.1 g of an aqueous 33.2% sodium methacrylate solution stabilized with 1.2 g of hydroquinone methyl ether is added, followed by introducing 8.8 g of tetra-n-butylammonium bromide (mole of 0.02 mol / sodium methacrylate). Thereafter, 193.2 g of ethyl chloroformate is introduced with stirring while maintaining the temperature of the medium at 20 ° C. (molar ratio of ethyl chloroformate / sodium methacrylate = 1.3).

The reaction mixture is left to stir while controlling the temperature to 20 ° C. The reaction progress is monitored by analyzing the residual sodium methacrylate in the aqueous phase separated by precipitation (the phases of the mixture are separated by precipitation as soon as stirring is stopped). After 3 hours of reaction, the degree of conversion of sodium methacrylate is greater than 99%. The reactor is then emptied and the phases of the reaction mixture are separated by precipitation at room temperature, the organic phase is washed with 57 g of water and the washed organic phase is separated by precipitation.

Thus, 234.5 g of the washed crude product is recovered and the product is stabilized by 0.02 g of di-tert-butyl-para-cresol. Perchlorate is removed under vacuum using a rotary evaporator at a temperature below 35 ° C.

198 g of carboethoxymethacrylic anhydride are obtained, the NMR purity of this material is shown in Table 2 below with yield.

Examples 7, 8 (comparative) and 9 (comparative)

Example 6 is repeated while changing the molar ratio of ethyl chloroformate / sodium methacrylate.

The results are shown in Table 2.

Example 6 7 8 (Comparative Example) 9 (Comparative Example) Molar ratio of ethyl chloroformate / sodium methacrylate 1.3 1.15 1.05 1.1 Composition (% by weight) of final product · Carboethoxy methacrylate anhydride · Methacrylic anhydride ㆍ Ethyl methacrylate 93.55.51 9091 6519286 8010253 Yield of Carboethoxymethacrylic Anhydride to Sodium Methacrylate 85.5 80

When the molar ratio of chloroformate / methacrylate is less than 1.15, poor selectivity to carboethoxymethacrylic anhydride is observed. It is clearly impossible to obtain a product of good purity under such molar ratios.

Example 10

The process is carried out in the same apparatus as in Example 1.

309.3 g of an aqueous 33.5% sodium methacrylate solution stabilized with 0.8 g of hydroquinone methyl ether is added, followed by introducing 192 g of toluene, followed by 0.02 mol of tetrabromated tetra-n-butylammonium per mole of sodium methacrylate. While stirring, the temperature of the medium is adjusted to 15 ° C. while introducing 125.1 g of ethyl chloroformate (molar ratio of ethyl chloroformate / sodium methacrylate: 1.2).

The progress of the reaction is monitored as in Example 3. After 4 hours of reaction, the degree of conversion of sodium methacrylate is greater than 99%. The phase of the crude product is separated by precipitation, not by washing, and also volatiles are removed under vacuum at temperatures below 35 ° C.

NMR analysis of the product without volatiles is as follows:

ㆍ Carboethoxymethacrylic anhydride ......... 95.5%

Methacrylic anhydride ... 4.5%

The yield of carboethoxymethacrylic anhydride is 87.5%.

Example 11

Example 6 is repeated, using potassium methacrylate instead of sodium methacrylate, and working at 10 ° C.

The composition (% by weight) of the final product is as follows:

Carboethoxymethacrylic anhydride ... 93%

Methacrylic anhydride ........................ 6%

ㆍ ..............................One %

Examples 12-14

Working at 10 ° C., Example 6 is repeated while changing the properties of the phase transfer catalyst introduced in the amount of mole of 0.01 mol / sodium methacrylate.

The results are shown in Table 3.

Example 12 13 14 Phase transfer catalyst % Yield of final product (relative to converted sodium methacrylate) 94 97 99.5 Time taken for the conversion of sodium methacrylate to exceed 98.5% 4.5 hours 3 hours 1.5 hours Composition (% by weight) of final product · Carboethoxymethacrylic anhydride · Methacrylic anhydride · 9442 946 9631

Claims (11)

In the preparation of high-purity (meth) acrylic anhydride represented by the following formula (I), [Formula I] (Wherein R ¹ represents H or CH ₃ , R ² represents an alkyl, alkenyl, aryl, alkaryl or aralkyl moiety) A method of reacting an alkali metal (meth) acrylate salt of formula (II) with a chloroformate salt of formula (III), wherein the reaction is carried out in the absence of an amine in an aqueous medium, and the chloroformate (III) / alkali metal (meth) acrylate ( II) the production method characterized in that the molar ratio of 1.15 or more: [Formula II] (Wherein R ¹ is as described above, M is an alkali metal), [Formula III] Wherein R ² is as described above. The process according to claim 1, wherein the reaction is carried out with compounds (II) and (III) as follows: R ² is C ₁ -C ₄₀ alkyl, C ₂ -C ₄₀ alkenyl, phenyl, phenyl (C ₁ -C ₄₀ alkyl) and (C ₁ -C ₄₀ alkyl) phenyl residues M represents sodium or potassium. The process according to claim 1 or 2, wherein the molar ratio of chloroformate (III) / alkali metal (meth) acrylate (II) is from 1.15 to 2, preferably from 1.5 to 1.7. 4. Process according to any one of the preceding claims, characterized in that the reaction is carried out at a temperature of -10 to +30 ° C, preferably +10 to +20 ° C. The chloroformate (III) is an alkali metal (meth) acrylic acid according to any one of claims 1 to 4, after neutralizing (meth) acrylic acid with peroxide MOH to produce alkali metal (meth) acrylate (II). A method characterized by reacting with acid salt (II), wherein the molar ratio of MOH / (meth) acrylic acid is 1 to 1.5 and the weight ratio of water / alkali metal (meth) acrylate (II) is 1.5 to 7 . The method according to claim 5, wherein the molar ratio of MOH / (meth) acrylic acid (II) is 1 to 1.1 and the weight ratio of water / alkali metal (meth) acrylate (II) is 1.5 to 2. The reaction according to any one of claims 1 to 6, wherein the reaction between alkali metal (meth) acrylate (II) and chloroformate (III) is dissolved or fixed in the polymerization support, and the alkali metal (meth) acrylate ( Characterized in that it is carried out in the presence of a phase transfer catalyst used at a rate of 0.001 to 0.02 moles per mole of II), in particular 0.005 to 0.01 moles. 8. The process of claim 7, wherein the phase transfer catalyst is selected from quaternary ammonium salts, phosphonium salts, and crown ethers. The process according to any one of claims 1 to 8, wherein at the end of the reaction, when the catalyst is fixed to the polymerization support, the phases of the two-phase or three-phase reaction mixture are separated by precipitation at room temperature and freed. And water-washed at room temperature, wherein the organic phase containing mixed anhydride (I) and excess chloroformate (III) is freed of volatiles under vacuum at temperatures below 35 ° C. 10. The method according to any one of claims 1 to 9, wherein the at least one polymerization inhibitor is in a ratio of 500 to 5000 ppm, in particular 500 to 1000 ppm relative to (meth) acrylic acid which is an alkali metal (meth) acrylate (II) or a precursor thereof. To a reaction medium. The process according to claim 10, wherein the polymerization inhibitor is selected from hydroquinone methyl ether, hydroquinone, phenothiazine and di-tert-butyl-para-cresol.